The field of art to which the invention pertains comprises pressure gauges having a dampener operative to avoid transmitting shock pulsation or vibration forces from the condition sensitive element to the output indicia.
1. Background of the Invention
Pressure gauges are widely utilized in a myriad of different environments for commercial and industrial applications where measuring and indication of fluid pressure values is required. Values of pressure are usually displayed by a pointer in analog form. The primary sensing element of the gauge typically comprises a Bourdon tube having a free end that incurs a predictable displacement in response to pressure changes to which it is exposed. Typically, tube displacement is translated via a movement or amplifier to a rotatable pointer that is displaced opposite a dial of calibrated pressure values.
The gauge movement impresses the extent of tube deflection upon the indicator element which registers the value of force, pressure or condition. For accurate measurement, the responsive element must not only be sensitive to very small changes in value of the forces of pressures measured, but the deflection of the condition responsive element in response to such changes must be sufficiently minute that the indicator will legibly register a precise change in value. Accordingly, when the force or pressure to be measured is subject to rapid or violent pulsations, it can cause the gauge movement and indicator to vibrate or fluctuate. Under these conditions it is very difficult to measure accurately the average mean or peak value of the source as a result of the pulsations being impressed on the condition responsive element. Such vibration makes reading of the gauge difficult and may even cause misalignment of parts, thereby necessitating frequent readjustment. Moreover, it tends to result in excessive strain and wear on the gauge elements, thereby reducing the expectant life of the gauge.
2. Background of the Prior Art
The use of dampeners in gauges are well known as exemplified by the disclosures of U.S. Pat. Nos. 1,664,776; 1,874,765; 2,701,968; 2,796,765 3,335,609; 4,100,812 and 4,413,523. Thus, while various constructions of gauge dampeners are known, they tend to be of relatively complex construction and therefore relatively costly. Another approach has been to liquid fill the case, but this has proven to be expensive, heavy and troublesome with associated leakage and disposal problems.
Despite recognition of the foregoing, a much simpler and more economically feasible construction of gauge dampener has heretofore been unknown.
It is an object of the invention to provide a novel dampener construction for gauges to dampen undesirable vibration fluctuation forces internally imposed on the gauge.
It is a further object of the invention to effect the previous object with a construction that is economically advantageous compared with previous constructions utilized for that purpose.
It is a still further object of the invention to effect the previous objects with a dampener that functions in a highly efficient manner and yet is substantially maintenance free.
This invention relates to pressure gauge apparatus including novel dampener apparatus for eliminating the adverse effects of pulsation, and vibration forces, and the like received by the gauge. More specifically, the invention relates to such a dampener in a pressure gauge that is operative to absorb shock pulsation or vibration forces against being transmitted from the output of the condition responsive element to the output indicia of the gauge, commonly in the form of a pointer opposite a dial plate.
The foregoing is achieved in accordance herewith by means of a close fitting, dampener agent packed sleeve, ferrule, thimble, hub, cup, etc. of metal or plastic situated on the pointer shaft of the gauge. In a first embodiment, a T-shaped hub including an elongated shank is integrally secured to an end disc. The shank includes a central elongated bore in which to receive an extended end portion of the pointer shaft to be dampened and is sized to afford a loose but controlled clearance fit thereabout. Concomitantly, the disc is positioned against the interior face of the gauge housing in a dampener cushioning relation with a layer of dampener agent therebetween to be described.
In a second embodiment, a floating dampener agent cup or the like, preferably in the form of a ferrule of metal or plastic, is situated at an intermediate location on the pointer shaft. To achieve the desired dampening effect the floating ferrule encircles the shaft so as to afford a controlled clearance about the shaft and is similarly packed with a dampener agent of selected viscosity.
In a third embodiment, the dampener is formed of a hub of metal or plastic surrounding the pointer shaft between the pinion gear and the back face of the dial plate. A quantity of dampener agent, as before, is placed between the hub and the juxtaposed surfaces thereabout. Unlike the previous embodiments, this embodiment does not require any modification to the basic gauge construction.
The shaft receiving bore of each embodiment affords a controlled clearance relative to the received support shaft of between about 0.002 inches-0.030 inches with about 0.008 inches being optimum. The dampener agent pack is characterized preferably by a viscosity range of an oil from about 1 million centistokes to a grease consistency number of 144 per ASTM D 1403 (xc2xc scale cone penetration test). Optimum consistency is about number 190.
Still further embodiments are disclosed in which various structures such as a sleeve, hub, bushing, recess or the like surround the pointer shaft and define a clearance containing a reservoir of lubricant.
Any surrounding structures afford outside clearance of between about 0.009 inches-0.051 inches with an optimum of about 0.017 inches that is similarly packed with a dampener agent. be obtained without the complexity normally associated with dampener constructions of the prior art.
The above noted features and advantages of the invention as well as other superior aspects thereof will be further appreciated by those skilled in the art upon reading the detailed description that follows in conjunction with the drawings.